1. Field of the Invention
The present invention relates to a semiconductor device, and in particular, to a semiconductor device having a trench gate and a method for forming the same.
2. Description of the Related Art
Technology that includes high-voltage elements is implemented to integrated circuits with high voltages and high power. In order to achieve high-withstand voltage and high current, the flow of the driving current in a conventional power transistor is developed from a horizontal direction to a vertical direction. A metal oxide semiconductor field-effect transistor (MOSFET) having a trench gate has been developed that is capable of effectively reducing on-resistance (Ron) and processing high currents.
FIG. 1 is a top view of a conventional metal oxide semiconductor field-effect transistor having a trench gate. The metal oxide semiconductor field-effect transistor comprises a substrate 500. A drain-doped region 510, a trench-gate structure 520 and source-doped regions 530 are in the substrate 500. The source-doped regions 530 are at two sides of the trench-gate structure 520. The source-doped regions 530 and the trench-gate structure 520 are connected to each other and have the same length, but the trench-gate structure 520 has a depth that is greater than that of the source-doped regions 530. An extending direction of length of the trench-gate structure 520 is parallel to that of the drain-doped region 510 as viewed from a top view perspective. The driving current of the metal oxide semiconductor field-effect transistor flows from the drain-doped region 510 towards the source-doped regions 530 and the trench-gate structure 520, and further flows up to the source-doped regions 530 along a sidewall of the trench-gate structure 520. Accordingly, the gate channel width w of the metal oxide semiconductor field-effect transistor is the length of the trench-gate structure 520.
When the gate channel length is fixed, the amount of driving current is proportional to the above-mentioned gate channel width. However, if the gate channel width is increased, the length of the trench-gate structure 520 is also increased, thereby increasing the size of the semiconductor device.
Thus, there exists a need in the art for development of a semiconductor device having a trench gate and a method for forming the same capable of mitigating or eliminating the aforementioned problems.